National Association of Conservation Districts

TMDL Case Study: Wisconsin

Lake Mendota, Wisconsin
Watershed Water Quality Case Study

The Lake Mendota watershed is located in Dane and Columbia Counties, in the lower central part of Wisconsin. The Dane and Columbia County Land Conservation Districts (LCD) have provided an excellent example of leadership in an effort begun in 1994 to establish watershed plans for sediment and phosphorus, an implementation strategy that is 30% complete, with strong public support for addressing the water quality needs of this priority watershed. Although it is not on the Section 303(d) list for Wisconsin, and therefore, does not require a total maximum daily load (TMDL) analysis, the process undertaken for Lake Mendota is an excellent example of how a TMDL process should work.

Background

Dane County is the second largest metropolitan area in Wisconsin, containing the city of Madison. It has 407,584 residents with a 20% increase expected by 2020. Located in north central Dane County and a portion of the southern part of Columbia County, the Lake Mendota watershed covers approximately 230 sq. miles or 153,000 acres in the Lower Rock River Basin and is comprised of two main subwatersheds: Yahara-Mendota and Six Mile-Pheasant Branch Creek. Pheasant Branch Creek, Dorn Creek, Six Mile Creek, Token Creek and the Yahara River are the five major Lake Mendota tributaries. Each suffers from polluted runoff.

Dane County contains 88% of the watershed or approximately 138,000 acres. The watershed is largely agricultural (53%) with the average farmer managing 229 dairy animals, 358 acres of corn and 142 acres of alfalfa. The Columbia County portion of the watershed contains nearly 15,000 acres, of which 87% is agricultural.

Lake Mendota, a 10,000-acre glacier lake, is intensively used for recreational purposes. Most of the lake’s water quality problems are linked to current and past rural and urban runoff carrying sediment, nutrients and toxins. About half of the original wetlands in the watershed have been drained or filled; existing wetlands cover approximately 6% of the watershed. Several wetlands and tributaries have been identified for restoration and enhancement. By implementing BMPs, nutrients and sediment loading to Lake Mendota will be reduced.

Wisconsin’s 71 LCD’s are somewhat unique from the rest of the 3,000 conservation districts in America. In 1982, state law changed the district structure from a political subdivision of the state to a unit of county government. Each LCD is governed by a Land Conservation Committee, most of the members of which are appointed from the County Board, the county government’s legislative branch.

Kevin Connors, the Dane County LCD County Conservationist, heads up a staff of 14 who works closely with two employees of the USDA-Natural Resources Conservation Service (NRCS). Their fieldwork is predominantly agricultural, but since 1999, four municipalities in the county have contracted with the LCD to also review erosion control plans for construction sites and provide inspection services. Municipal government provides enforcement action. Urban development covers 20% of the watershed and has been growing steadily for the last several decades. Kurt Calkins, County Conservationist, manages Columbia LCD, with a staff of seven.

Teamwork

With overall leadership provided by the Wisconsin Department of Natural Resources (WDNR), the LCDs were a part of a strong partnership with NRCS, Extension, the Wisconsin Department of Agriculture and the University of Wisconsin. Three teams were established: a land team, a water team and an information and education team.

The Land Team

The LCDs collected data from 1994 through 1996 on agricultural lands, barnyards and urban areas in the watershed. The data were used to estimate the nonpoint pollutant loads. The land team used the NRCS Universal Soil Loss Equation, the Dane County database program similar to the NRCS ‘FOCS’ program and the WDNR Win Husle Model for sediment and phosphorus delivery to Lake Mendota’s tributaries. The team’s investigation included an inventory of all the livestock feedlots in the watershed, upland sediment delivery, streambank erosion, wetlands, the urban areas and construction sites.

The team’s upland sediment inventory estimated over 35,000 tons of sediment were being delivered annually to streams; and, over 6,500 tons reached the lake each year. The primary source of sediment loading was cropland. Streambank erosion was minimal.

Through the land team’s modeling and analysis efforts, they estimated a delivery of 76,000 pounds of phosphorus to the Lake annually from the collective results of inventories of nutrient management, feedlots, upland sediment and streambank erosion. Their estimate was within 8% of the data maintained from monitoring stations that had been in place for several decades.

The Water Team

The water team led by the University focused on monitoring water quality data from the Lake. Stream monitoring stations have been in active use since the 1970’s and have provided an excellent and substantial measure of past and current trends. The team also conducted a groundwater survey. They publicized their intention to test well water, conducted public meetings and handed out sample bottles. Through a mass sampling analysis of samples of 157 wells, results showed that 60% of the wells in the watershed exceeded acceptable nitrate levels.

Setting Goals

After analyzing the data, the water team noted that with the current level of phosphorus loading, they observed the presence of blue-green algae blooms on an average of four out of five days. If the daily loads of phosphorus could be reduced by 36,000 pounds a year, approximately a 50% reduction, the algae blooms would decrease to one day out of five.

The land team set standards for the major land uses in the watershed. For cropland, the goal was to reduce erosion rates to "T", the tolerable soil loss established by the county soil survey for each individual soil type. For feedlots, the threshold level was set at 200 pounds of phosphorus per year, above which additional treatment would be required. Of the 400 feedlots in the watershed, ten critical sites exceeded the standard. Primary practices to manage feedlot runoff would include "clean water diversions" such as gutters, downspouts, swales or diversions that would redirect clean water away from feedlots, thereby reducing the amount of polluted runoff flowing to streams during storm events.

Criteria for urban sites was developed based on modeling done in the initial planning phase. For active construction sites, a county ordinance had already set the standard of a maximum of 7.5 tons of sediment per acre per year. All erosion and sediment control plans must be designed to meet that standard in order to be approved by the LCD prior to the County’s issuance of grading and building permits.

Public Involvement

The partners realized that strong public support was essential to the success of the project. They formed the Citizens Advisory Committee in 1997, representing a cross-section of citizens including farmers, developers, teachers and government. The Committee, like most watershed groups, got beyond the phase where it was assumed that "the other guy" was causing the problems and became effective as stakeholders who accept their own responsibility for pollutant contribution and agree to work together to solve their collective problems. Meetings included presentations from various experts. For example, the banking community, both agricultural and urban lenders, gave one presentation. "The Citizens Advisory Committee serves as the eyes and ears of the project," said Kevin Connors. "They have kept us informed of reactions and opinions from the community and they provided valuable input on proposed rules, regulations and our implementation strategy."

A Work in Progress

The Lake Mendota Watershed Project is an excellent example of locally-led conservation. In 2001, the project still has a way to go. In large part, the success of the project has been due to key partners working well together with strong leadership from the land conservation districts. Little would have changed in the development and implementation of the watershed plan to reduce sediment and phosphorus if actual TMDLs had been developed.

Contact:

Dane County LCD – Kevin Connors, connors.kevin@co.dane.wi.us , 608-224-3730